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Select with long list

Posts: 12
in Command Line

I'm writing a command line script, where I want the user to select a file name. The select command almost does the job, but the list of files is rather long, about 150.

Anyone know of a way of throwing something like less into the mix, to enable the user to scroll around the list before selecting?

Cheers.

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  • Posts: 647
    dwclarke wrote:
    I'm writing a command line script, where I want the user to select a file name. The select command almost does the job, but the list of files is rather long, about 150.

    Anyone know of a way of throwing something like less into the mix, to enable the user to scroll around the list before selecting?

    Cheers.

    Select is rather strict and unflexible. You can relay on the usual buffer of any terminal (scrolling with SHIFT+PgUp/PgDown ).

    You are better off writting your own menu though

    Regards
  • Posts: 216
    dwclarke wrote:
    I'm writing a command line script, where I want the user to select a file name. The select command almost does the job, but the list of files is rather long, about 150.

    Anyone know of a way of throwing something like less into the mix, to enable the user to scroll around the list before selecting?

    Cheers.
    I've never used select before, but I do use Bash's builtin read function, in conjunction with a loop, to do this very thing. something like this might work: 
    1. #!/bin/bash
    2. listfiles(){
    3.   vars=`seq 1 150`
    4.   for var in $vars; do
    5.     echo $var
    6.   done
    7. }
    8. listfiles|more
    9. until [ -n "$answer" ]; do
    10.   echo -n "Enter your selection: "
    11.   read answer
    12. done
    13. echo you selected $answer

    just replace the vars= line with your 150 variables. btw, i used more instead of less - personal pref.

    -bill
  • Posts: 12
    Thanks for that. I've moded it a bit, and have ended up with this:
    1. #!/bin/bash 
    2. # Script for a user to select a file
    3.  
    4. echo "Remember the number of the file you want, then press 'q', and enter the number"
    5. echo "Press any key to start"
    6.  
    7. # Wait for keypress
    8. read -n 1 -s 
    9.  
    10. # Show numerated file list
    11. ls *.txt | cat -n | less
    12.  
    13. #Get users file selection number
    14. until [ -n "$answer" ]; do 
    15.   echo -n "Enter your selection: " 
    16.   read answer 
    17. done
    18.  
    19. # Check entry is numeric
    20. if echo $answer | grep "^[0-9]*$" > /dev/null
    21. then
    22.  
    23.  # check the number isn't bigger than the list of files
    24.  count=`ls *.txt | wc -l`
    25.  if [ $answer -le $count ]
    26.  then
    27.  
    28.    ourfile=`ls *.txt | sed -n "$answer p"`
    29.    echo "You chose $ourfile"
    30.  
    31.  else
    32.   echo "Number is too large"
    33.  fi
    34.  
    35. else
    36.  echo "$answer is not numeric"
    37. fi
  • Posts: 1,114
    I think I learn more from this sub-forum than any of the others. Thanks to all that post code here. As someone who never had to write bash code, I like watching others discuss it.
  • Posts: 647
    If I may add some suggestions:
    1. # Show numerated file list
    2. ls *.txt | cat -n | less

    Yo do not need to pipe anything here, just do
    1. less -N *.txt
    1. # Check entry is numeric
    2. if echo $answer | grep "^[0-9]*$" > /dev/null

    Again, you do not need to pipe anything. This checks if it contains non numeric characters: a2 or 34s will fail the test
    1. if [[ ! $answer = *[!0-9]* [[
    1.  # check the number isn't bigger than the list of files
    2.  count=`ls *.txt | wc -l`

    Don't ever parse the output of ls!!!. Insted: 
    1. f=(*.txt)
    2. count=${#f[@]}

    WARNING: this does not check if there are no .txt files <--- it will fail in that case as it will return a one file (the * glob)
    1.    ourfile=`ls *.txt | sed -n "$answer p"`
    2.    echo "You chose $ourfile"

    I'm not quite sure what's your intention here... ;)

    I'm assuming you are using bash, aren't you?

    You should avoid `command` as it is deprecated and not easy to nest (try nesting 3-4 things and you'll understand what I mean). Try $(command) instead ;)

    If you are using bash.... you should use [ [ instead of [ . The [ command (yes, it is a command, not a built in shell option) is, by far, less powerfull than the built in [ [

    Regards
  • Posts: 12
    Thanks for your substantial suggestions, it's been very educational. I'll go through the bits:

    marc wrote:
    If I may add some suggestions:
    1. # Show numerated file list
    2. ls *.txt | cat -n | less

    Yo do not need to pipe anything here, just do
    1. less -N *.txt

    Your suggestion gave me the contents of the files, whereas I need to search through the file names, to pick one. I did use the -N for less, though, to give me:
    1. # Show numerated file list
    2. ls *.txt | less -N
    1. # Check entry is numeric
    2. if echo $answer | grep "^[0-9]*$" > /dev/null

    Again, you do not need to pipe anything. This checks if it contains non numeric characters: a2 or 34s will fail the test
    1. if &#91;&#91; ! $answer = *[!0-9]* &#91;&#91;

    Of course, much simpler, although, should that be '==' not '='?. While Googling, I also found the similar
    1.  if &#91;&#91; $answer =~ ^[0-9]+$ &#91;&#91;;

    Which gets rid of the double negation.
    1.  # check the number isn't bigger than the list of files
    2.  count=`ls *.txt | wc -l`

    Don't ever parse the output of ls!!!. Insted: 
    1. f=(*.txt)
    2. count=${#f[@]}

    That works for me, although I'm interested as to why the output of ls shouldn't be used for parsing (besides being unnecessary)
    WARNING: this does not check if there are no .txt files <--- it will fail in that case as it will return a one file (the * glob)

    Luckily I do this earlier, in an unshown part of the code.
    1.    ourfile=`ls *.txt | sed -n "$answer p"`
    2.    echo "You chose $ourfile"

    I'm not quite sure what's your intention here... ;)

    This takes the number, and converts it into the filename we've picked. With what you've just taught me, I should be able to simplify this.
    I'm assuming you are using bash, aren't you?

    Yup
    You should avoid `command` as it is deprecated and not easy to nest (try nesting 3-4 things and you'll understand what I mean). Try $(command) instead ;)
    [\quote]

    I didn't know that. I've been using the Bash Beginners Guide and Advanced Bash Scripting Guide for my main references.
    show previous quotes

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